public interface

ScriptEngine

javax.script.ScriptEngine
Known Indirect Subclasses

Class Overview

ScriptEngine is the fundamental interface whose methods must be fully functional in every implementation of this specification.

These methods provide basic scripting functionality. Applications written to this simple interface are expected to work with minimal modifications in every implementation. It includes methods that execute scripts, and ones that set and get values.

The values are key/value pairs of two types. The first type of pairs consists of those whose keys are reserved and defined in this specification or by individual implementations. The values in the pairs with reserved keys have specified meanings.

The other type of pairs consists of those that create Java language Bindings, the values are usually represented in scripts by the corresponding keys or by decorated forms of them.

Summary

Constants
String ARGV Reserved key for a named value that passes an array of positional arguments to a script.
String ENGINE Reserved key for a named value that is the name of the ScriptEngine implementation.
String ENGINE_VERSION Reserved key for a named value that identifies the version of the ScriptEngine implementation.
String FILENAME Reserved key for a named value that is the name of the file being executed.
String LANGUAGE Reserved key for a named value that is the full name of Scripting Language supported by the implementation.
String LANGUAGE_VERSION Reserved key for the named value that identifies the version of the scripting language supported by the implementation.
String NAME Reserved key for a named value that identifies the short name of the scripting language.
Public Methods
abstract Bindings createBindings()
Returns an uninitialized Bindings.
abstract Object eval(String script, Bindings n)
Executes the script using the Bindings argument as the ENGINE_SCOPE Bindings of the ScriptEngine during the script execution.
abstract Object eval(Reader reader, Bindings n)
Same as eval(String, Bindings) except that the source of the script is provided as a Reader.
abstract Object eval(Reader reader)
Same as eval(String) except that the source of the script is provided as a Reader
abstract Object eval(Reader reader, ScriptContext context)
Same as eval(String, ScriptContext) where the source of the script is read from a Reader.
abstract Object eval(String script, ScriptContext context)
Causes the immediate execution of the script whose source is the String passed as the first argument.
abstract Object eval(String script)
Executes the specified script.
abstract Object get(String key)
Retrieves a value set in the state of this engine.
abstract Bindings getBindings(int scope)
Returns a scope of named values.
abstract ScriptContext getContext()
Returns the default ScriptContext of the ScriptEngine whose Bindings, Reader and Writers are used for script executions when no ScriptContext is specified.
abstract ScriptEngineFactory getFactory()
Returns a ScriptEngineFactory for the class to which this ScriptEngine belongs.
abstract void put(String key, Object value)
Sets a key/value pair in the state of the ScriptEngine that may either create a Java Language Binding to be used in the execution of scripts or be used in some other way, depending on whether the key is reserved.
abstract void setBindings(Bindings bindings, int scope)
Sets a scope of named values to be used by scripts.
abstract void setContext(ScriptContext context)
Sets the default ScriptContext of the ScriptEngine whose Bindings, Reader and Writers are used for script executions when no ScriptContext is specified.

Constants

public static final String ARGV

Reserved key for a named value that passes an array of positional arguments to a script.

Constant Value: "javax.script.argv"

public static final String ENGINE

Reserved key for a named value that is the name of the ScriptEngine implementation.

Constant Value: "javax.script.engine"

public static final String ENGINE_VERSION

Reserved key for a named value that identifies the version of the ScriptEngine implementation.

Constant Value: "javax.script.engine_version"

public static final String FILENAME

Reserved key for a named value that is the name of the file being executed.

Constant Value: "javax.script.filename"

public static final String LANGUAGE

Reserved key for a named value that is the full name of Scripting Language supported by the implementation.

Constant Value: "javax.script.language"

public static final String LANGUAGE_VERSION

Reserved key for the named value that identifies the version of the scripting language supported by the implementation.

Constant Value: "javax.script.language_version"

public static final String NAME

Reserved key for a named value that identifies the short name of the scripting language. The name is used by the ScriptEngineManager to locate a ScriptEngine with a given name in the getEngineByName method.

Constant Value: "javax.script.name"

Public Methods

public abstract Bindings createBindings ()

Returns an uninitialized Bindings.

Returns
  • A Bindings that can be used to replace the state of this ScriptEngine.

public abstract Object eval (String script, Bindings n)

Executes the script using the Bindings argument as the ENGINE_SCOPE Bindings of the ScriptEngine during the script execution. The Reader, Writer and non-ENGINE_SCOPE Bindings of the default ScriptContext are used. The ENGINE_SCOPE Bindings of the ScriptEngine is not changed, and its mappings are unaltered by the script execution.

Parameters
script The source for the script.
n The Bindings of attributes to be used for script execution.
Returns
  • The value returned by the script.
Throws
ScriptException if an error occurrs in script.
NullPointerException if either argument is null.

public abstract Object eval (Reader reader, Bindings n)

Same as eval(String, Bindings) except that the source of the script is provided as a Reader.

Parameters
reader The source of the script.
n The Bindings of attributes.
Returns
  • The value returned by the script.
Throws
ScriptException if an error occurrs.
NullPointerException if either argument is null.

public abstract Object eval (Reader reader)

Same as eval(String) except that the source of the script is provided as a Reader

Parameters
reader The source of the script.
Returns
  • The value returned by the script.
Throws
ScriptException if an error occurrs in script.
NullPointerException if the argument is null.

public abstract Object eval (Reader reader, ScriptContext context)

Same as eval(String, ScriptContext) where the source of the script is read from a Reader.

Parameters
reader The source of the script to be executed by the script engine.
context The ScriptContext passed to the script engine.
Returns
  • The value returned from the execution of the script.
Throws
ScriptException if an error occurrs in script.
NullPointerException if either argument is null.

public abstract Object eval (String script, ScriptContext context)

Causes the immediate execution of the script whose source is the String passed as the first argument. The script may be reparsed or recompiled before execution. State left in the engine from previous executions, including variable values and compiled procedures may be visible during this execution.

Parameters
script The script to be executed by the script engine.
context A ScriptContext exposing sets of attributes in different scopes. The meanings of the scopes ScriptContext.GLOBAL_SCOPE, and ScriptContext.ENGINE_SCOPE are defined in the specification.

The ENGINE_SCOPE Bindings of the ScriptContext contains the bindings of scripting variables to application objects to be used during this script execution.
Returns
  • The value returned from the execution of the script.
Throws
ScriptException if an error occurrs in script. ScriptEngines should create and throw ScriptException wrappers for checked Exceptions thrown by underlying scripting implementations.
NullPointerException if either argument is null.

public abstract Object eval (String script)

Executes the specified script. The default ScriptContext for the ScriptEngine is used.

Parameters
script The script language source to be executed.
Returns
  • The value returned from the execution of the script.
Throws
ScriptException if error occurrs in script.
NullPointerException if the argument is null.

public abstract Object get (String key)

Retrieves a value set in the state of this engine. The value might be one which was set using setValue or some other value in the state of the ScriptEngine, depending on the implementation. Must have the same effect as getBindings(ScriptContext.ENGINE_SCOPE).get

Parameters
key The key whose value is to be returned
Returns
  • the value for the given key
Throws
NullPointerException if key is null.
IllegalArgumentException if key is empty.

public abstract Bindings getBindings (int scope)

Returns a scope of named values. The possible scopes are:

  • ScriptContext.GLOBAL_SCOPE - The set of named values representing global scope. If this ScriptEngine is created by a ScriptEngineManager, then the manager sets global scope bindings. This may be null if no global scope is associated with this ScriptEngine
  • ScriptContext.ENGINE_SCOPE - The set of named values representing the state of this ScriptEngine. The values are generally visible in scripts using the associated keys as variable names.
  • Any other value of scope defined in the default ScriptContext of the ScriptEngine.


The Bindings instances that are returned must be identical to those returned by the getBindings method of ScriptContext called with corresponding arguments on the default ScriptContext of the ScriptEngine.

Parameters
scope Either ScriptContext.ENGINE_SCOPE or ScriptContext.GLOBAL_SCOPE which specifies the Bindings to return. Implementations of ScriptContext may define additional scopes. If the default ScriptContext of the ScriptEngine defines additional scopes, any of them can be passed to get the corresponding Bindings.
Returns
  • The Bindings with the specified scope.
Throws
IllegalArgumentException if specified scope is invalid

public abstract ScriptContext getContext ()

Returns the default ScriptContext of the ScriptEngine whose Bindings, Reader and Writers are used for script executions when no ScriptContext is specified.

Returns
  • The default ScriptContext of the ScriptEngine.

public abstract ScriptEngineFactory getFactory ()

Returns a ScriptEngineFactory for the class to which this ScriptEngine belongs.

Returns
  • The ScriptEngineFactory

public abstract void put (String key, Object value)

Sets a key/value pair in the state of the ScriptEngine that may either create a Java Language Binding to be used in the execution of scripts or be used in some other way, depending on whether the key is reserved. Must have the same effect as getBindings(ScriptContext.ENGINE_SCOPE).put.

Parameters
key The name of named value to add
value The value of named value to add.
Throws
NullPointerException if key is null.
IllegalArgumentException if key is empty.

public abstract void setBindings (Bindings bindings, int scope)

Sets a scope of named values to be used by scripts. The possible scopes are:

  • ScriptContext.ENGINE_SCOPE - The specified Bindings replaces the engine scope of the ScriptEngine.
  • ScriptContext.GLOBAL_SCOPE - The specified Bindings must be visible as the GLOBAL_SCOPE.
  • Any other value of scope defined in the default ScriptContext of the ScriptEngine.


The method must have the same effect as calling the setBindings method of ScriptContext with the corresponding value of scope on the default ScriptContext of the ScriptEngine.

Parameters
bindings The Bindings for the specified scope.
scope The specified scope. Either ScriptContext.ENGINE_SCOPE, ScriptContext.GLOBAL_SCOPE, or any other valid value of scope.
Throws
IllegalArgumentException if the scope is invalid
NullPointerException if the bindings is null and the scope is ScriptContext.ENGINE_SCOPE

public abstract void setContext (ScriptContext context)

Sets the default ScriptContext of the ScriptEngine whose Bindings, Reader and Writers are used for script executions when no ScriptContext is specified.

Parameters
context A ScriptContext that will replace the default ScriptContext in the ScriptEngine.
Throws
NullPointerException if context is null.